Does anoxia affect organic matter preservation Diagenesis and burial of the major biochemicals under oxic and anoxic depositional conditions
- Univ. of British Columbia, Vancouver (Canada). Dept. of Oceanography
- Univ. of Washington, Seattle, WA (United States). School of Oceanography
The role of anoxia in organic matter (OM) preservation in coastal sediments is tested directly using sediment trap and core samples from Dabob Bay (Washington State) and Saanich Inlet (British Columbia). These sites are similar in productivity, OM sources and sedimentation rates, but differ in that Dabob Bay bottom waters are permanently oxygenated whereas those of Saanich Inlet are anoxic except for occasional autumn flushing events. Samples were analyzed for organic carbon, nitrogen, amino acids, neutral sugars and lignin. Mixed terrigenous and marine OM sources are indicated at both sites, but there is a lower terrigenous OM contribution in Saanich Inlet than in Dabob Bay. Major, highly selective OM losses occur at the benthic interface of both sites with very similar reactivity patterns. The following general order of reactivity, equivalent to preferential loss of marine OM, is observed: total amino acids > total sugars [ge] nitrogen > organic carbon > lignin. Sedimentary diagenesis is less selective and less extensive, and in Dabob Bay is largely masked by bioturbation. Calculated biochemical losses at the benthic interface are consistently higher in Dabob Bay, possibly suggesting uniformly higher degradation rates under aerobic conditions, but most readily explained by mixing of surficial sediments. At both sites, there are also clear differences in calculated burial efficiency among the various measured OM components. However, despite OM source differences, burial efficiency values at the two sites are indistinguishable. These results indicate that anoxia ultimately has no measurable effect on OM preservation at these sites.
- OSTI ID:
- 5974337
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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